The present invention is in the field of mechanical linkages, and more particularly, relates to linkages for constraining relatively large motion of the reference member to be along a reference axis.
Linkages for constraining motion of an element to be along a reference axis are particularly useful in weighing systems, or scales, where it is desired to sense the weight of an object. Such systems require transfer of the gravitational force of the object to a force sensor without the introduction of error components due to friction and other sources. Typically, in the prior art, this function is established by a basically parallelogram linkage. In one form, a pair of V-shaped flexure (or hinged) elements, each having a vertex portion and a pair of distal end portions, is configured with the distal end portions being affixed to a support member or casing, so that the V-shaped members lie in parallel planes. A connecting link is fastened between the vertex portions of the flexure elements. With this configuration, in order to precisely constrain the motion of the reference member coupled to the link to a motion along that reference axis, the V-shaped elements must be precisely positioned with respect to the support member in order to achieve the desired parallelism. As a practical matter, this requires critical alignment of the flexure elements during the fastening of the distal ends of those elements to the support member. Even with such precise positioning of the flexure elements, the range of motion for which the reference member follows the reference axis is relatively limited. Moreover, with large motions, there is also substantial side motion of the reference member.
It is an object of the present invention to provide an improved linkage for constraining the motion of an element to motion along a reference axis with a relatively large range of motion.